Fix PPLT metric for the new TabContents based prerendering

chrome/browser/prerender/prerender_observer.cc

 // Copyright (c) 2011 The Chromium Authors. All rights reserved.
 // Use of this source code is governed by a BSD-style license that can be
 // found in the LICENSE file.
 
 #include "chrome/browser/prerender/prerender_observer.h"
 
 #include "base/time.h"
 #include "chrome/browser/prerender/prerender_manager.h"
 #include "chrome/browser/profiles/profile.h"
 #include "content/browser/tab_contents/tab_contents.h"
@@ skipping 26 matching lines @@
     IPC_MESSAGE_HANDLER(ViewHostMsg_DidStartProvisionalLoadForFrame,
                         OnDidStartProvisionalLoadForFrame)
   IPC_END_MESSAGE_MAP()
   return false;
 }
 
 void PrerenderObserver::OnDidStartProvisionalLoadForFrame(int64 frame_id,
                                                           bool is_main_frame,
                                                           bool has_opener_set,
                                                           const GURL& url) {
-  // Don't include prerendered pages in the PPLT metric until after they are
-  // swapped in.
-  if (IsPrerendering())
-    return;
   if (is_main_frame) {
     // Record the beginning of a new PPLT navigation.
     pplt_load_start_ = base::TimeTicks::Now();
   }
 }
 
 void PrerenderObserver::DidStopLoading() {
   // Don't include prerendered pages in the PPLT metric until after they are
   // swapped in.
-  if (IsPrerendering())
-    return;
 
   // Compute the PPLT metric and report it in a histogram, if needed.
-  if (!pplt_load_start_.is_null()) {
+  if (!pplt_load_start_.is_null() && !IsPrerendering()) {
     PrerenderManager::RecordPerceivedPageLoadTime(
         base::TimeTicks::Now() - pplt_load_start_, tab_contents());
   }
 
   // Reset the PPLT metric.
   pplt_load_start_ = base::TimeTicks();
 }
 
 PrerenderManager* PrerenderObserver::MaybeGetPrerenderManager() {
   return tab_contents()->profile()->GetPrerenderManager();
@@ skipping 10 matching lines @@
                                                   has_opener_set);
 }
 
 bool PrerenderObserver::IsPrerendering() {
   PrerenderManager* prerender_manager = MaybeGetPrerenderManager();
   if (!prerender_manager)
     return false;
   return prerender_manager->IsTabContentsPrerendering(tab_contents());
 }
 
+void PrerenderObserver::PrerenderSwappedIn() {
+  // Ensure we are not prerendering any more.
+  DCHECK(!IsPrerendering());
+  if (pplt_load_start_.is_null()) {
+    // If we have already finished loading, report a 0 PPLT.
+    PrerenderManager::RecordPerceivedPageLoadTime(base::TimeDelta(),
+                                                  tab_contents());
+  } else {
+    // If we have not finished loading yet, rebase the start time to now.
+    pplt_load_start_ = base::TimeTicks::Now();
+  }
+}
+
 }  // namespace prerender